Do Early Warning Scores predict mortality in adult ED patients?

Three Part Question

In [adult ED patients] do [Early Warning Scores] predict [mortality]?

Clinical Scenario

Whilst working in the Emergency Department you assess a 44 year old male patient with a large intracerebral haemorrhage. He only scores 2 on his early warning score due to his decreased level of consciousness, his other physiological variables being normal. Based on clinical indications, he is intubated and ventilated and taken to intensive care but dies two days later. Whilst reflecting on this case you wonder whether early warning scores are sensitive and specific enough to predict mortality in ED patients.

Search Strategy

A combined database search of Cinahl (1981 to present), Embase (1980 to present) and Medline (1950 to present from PubMed) was carried out using NHS Evidence Health Information Resources. The following search terms were used: {[scoring systems].ti,ab OR [track and trigger].ti,ab OR [mortality prediction].ti,ab OR [early warning scores].ti,ab OR [MEWS].ti,ab OR [rapid emergency medicine score or [REMS].ti,ab} AND {[emergency medicine].ti,ab OR [emergency department].ti,ab}. No limits were placed on the search.

Search Outcome

Altogether a total of 144 papers were identified, of which 10 were relevant to the study question. These are shown in the table

Relevant Paper(s)

Author, date and country

Patient group

Study type (level of evidence)

Outcomes

Key results

Study Weaknesses

Olsson et al2004Sweden

11,751 consecutive non-surgical patients presenting to the ED

Prospective cohort

In-hospital mortality

AUROC REMS: 0.852 (SEM ± 0.014)

Single-centre study in a non-surgical ED. Data was 7-8 years old when published. No timing relating to mortality is given

Goodacre et al2006UK

5583 medical patients either admitted to hospital or died in ED

Secondary analysis

In-hospital mortality

AUROC REMS: 0.74 (95% CI 0.70-0.78)

Large amount of missing data (REMS only calculated in 39.7% of patients). Not all emergency medical admissions were included. Ambulance data rather than first ED recording

Howell et al2007USA

2132 ED patients with an diagnosis of infection or possible infection

Prospective cohort

28-day in-hospital mortality

AUROC REMS: 0.802 (95% CI 0.752-0.852)

Only patients with infection were included. Missing or inaccurate admission data. Modified version of REMS

Secondary outcome (30-day mortality)used. No use of split sample technique for a derivation study. Only resuscitation room patients used. Data collection from patient documentation. No mention of availability of data given. Small numbers. Patients identified over a single month

Comment(s)

Both MEWS and REMS can predict mortality in adult ED patients. Area under ROC curve was, on the whole, better for REMS than MEWS (0.74-0.911 compared with 0.67-0.8)
If it is generally accepted that an AUROC of ≥0.8 has good predictive value, then REMS reaches this target in 3 papers and MEWS in only one. However in the only paper to directly compare the two scoring systems, AUROC for 30-day mortality was almost the same: REMS 0.771 and MEWS 0.75413.
REMS is a score derived from ED patients; it was compiled using a split-sample method which is the method generally accepted by the medical community as standard. It was then validated in a further study of almost twelve thousand patients by the same authors, much greater numbers than the work involving MEWS
Ideally REMS needs to be validated in a multi-centre UK ED population. The future probably lies in a modified version of REMS that is appropriate to the local population and a method of calculating it more easily.

Clinical Bottom Line

It must be remembered that critically ill patients may have a low early warning score and that EWS should be used alongside, rather than as a replacement for senior clinical expertise